heater control for curing oven

I'm into recumbents and am exploring building a mold for a prepreg
carbon setup. This looks like an active site for composites.

Can anyone recommend a heater control to adjust the heating/cooling
ramp rate (5 degrees a minute, etc)? I'm obviously trying to keep
costs down so something surplus or homemade would be best.

Also, if I do a pressure bladder inside a female mold how do I apply
the vacuum between the composite and the inner mold line (so that the
bladder inflates)? Or should I just only apply pressure to the bladder
and not try to pull a vacuum on the mold?

Thanks airplane guys.

Joe

Check both the Grainger and McMaster Carr listings. They both have
fairly reasonably priced ($90- $400) temperature controlers that can be
programed with ramp rates and hold times. Add in a solid state relay
and a thermocouple (another $40) and you can build a nice curing oven.
They are simple to set up and use. Eurotherm is one brand name that I
remember from my lab days........ http://www.eurotherm.com/
===============
Leon McAtee
Building bents for kids and experimenting with my first bent trike

Make your oven out of urethane foam insulation. Line it with aluminum
foil. Install 100 watt lightbulbs as needed to get the desired heatup
rate. I used 8 or 10. Put aluminum foil reflectors over the bulbs to
keep them from shining directly on the part and creating hot spots.
This is the oven I used to bond some honeycomb repairs to a Gulfstream
G-II flap, a 250° cure process. Of course, I used a hot bonder to
control and monitor it, but a simple thermostat would work just as well.

The biggest factor in your heatup rate will be the mass of your mold.
Less massive will make life easier. You'll need to have thermocouples
right on the part you're curing.

Don't use vacuum with a bladder. Apply pressure. About 2 atmospheres.
Make sure you consolidate your layup by applying pressure at
elevated temperature for a few hours before the cure cycle.

I have two Vision R-40's.

wrote:
I'm into recumbents and am exploring building a mold for a prepreg
carbon setup. This looks like an active site for composites.

Can anyone recommend a heater control to adjust the heating/cooling
ramp rate (5 degrees a minute, etc)? I'm obviously trying to keep
costs down so something surplus or homemade would be best.

Also, if I do a pressure bladder inside a female mold how do I apply
the vacuum between the composite and the inner mold line (so that the
bladder inflates)? Or should I just only apply pressure to the bladder
and not try to pull a vacuum on the mold?

Thanks airplane guys.

Joe



--
J Kimmel

www.metalinnovations.com

"Cuius testiculos habes, habeas cardia et cerebellum." - When you have
their full attention in your grip, their hearts and minds will follow.

Good info, thanks.

This post brings up a couple of questions...

1. Do I need breather with a bladder (to allow the air to be forced
out)?
2. Is there any concern with vapors building up in the oven and
causing a fire?
3. Perhaps it would be a good idea to put 2 bars in the bladder and
then put the whole thing in a vacuum bag so that the mold only sees
approximately 1 bar? This would keep the fumes out of the oven too.
4. Can thermocouples be joined together to "average" without using
software?
5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?

Thanks again folks.

Joe

wrote:
Good info, thanks.


5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?

Thanks again folks.

Joe

Try e-bay item 7546821715. I have one which I have used a couple of
times and am satisfied with.

Dan, U.S. Air Force, retired

"Dan, U.S. Air Force, retired" wrote in message news:1KiYe.29212$dm.24132@lakeread03...
wrote:
Good info, thanks.


5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?

Thanks again folks.

Joe

Try e-bay item 7546821715. I have one which I have used a couple of times and am satisfied with.

Dan, U.S. Air Force, retired

47 bucks delivered with the thermocouple! Does it do PID? Heck of a deal it looks like...

..Blueskies. wrote:
"Dan, U.S. Air Force, retired" wrote in message news:1KiYe.29212$dm.24132@lakeread03...

wrote:

Good info, thanks.


5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?

Thanks again folks.

Joe


Try e-bay item 7546821715. I have one which I have used a couple of times and am satisfied with.

Dan, U.S. Air Force, retired


47 bucks delivered with the thermocouple! Does it do PID? Heck of a deal it looks like...


I'd be able to answer if I knew what PID is.

Dan, U.S. Air Force, retired

In article .com,
wrote:


5. What is a very affordable PID controller (preferably under $100)
that will allow the ramp rate (up and down) to be set?



Joe

A stand alone, full PID with ramp and soak? Several hundred dollars, I'm
afraid. Keep an eye out on ebay, but the one Dan referenced isn't such a
beast.

Again, I have absolutely no idea what your requirements are as far as
accuracy and precision. If you can clarify those, you might find that
you need less sophistication. Also, as someone else mentioned, you might
find PC based software to do the work of a temperature controller. I
don't know what's out there in that regard.

Yaa, you would think that an I/O card (with the TC voltage coming in
and the voltage to the relay going out) could do this pretty easily and
you could just put in the "curve" you want in your PC program and it
would know how to get you there. Basically a PC software driven PID
using a cheap I/O card off the RS232.

I did a brief look but couldn't find anything though so it's no doubt
harder than I'm imagining it.

I did find some cool stuff on guys doing their own coffee roasting with
hot-air popcorn poppers They're using PIDs too.

Joe

If you want to try to "roll your own" you might check out basic stamps
- and the clones. I'm pretty sure that you could find some freeware
for these that does what you need.

http://www.parallax.com/
====================
Leon McAtee
having lots of fun with my bent trike............but need to get back
to work on the Quickie.